1. Field of the Invention
The invention relates to a turbine engine stator having pivoting blades and a control ring.
2. Discussion of the Background
Particularly for the high pressure stages of compressors, numerous turbine engines have stator blades, which are pivotable and not fixed in order to modify the characteristics of the straightening of the gases passing through the passage in which said blades extend. Such variable setting blades therefore incorporate pivots extending through an envelope, which defines the stream or passage and said pivots are connected to links, which are normally joined together by a control ring placed around the passage and a control mechanism displaces the same in translation along the axis of the turbine engine or in rotation about said axis. In both cases, the links rotate and drive the pivots of the blades.
A disadvantage of this system is that to the thrust of the gases producing significant forces and stresses on the blades. These stresses are transmitted to the pivots and to the bearings of the envelope supporting the same and have a preferred direction. The friction exerted by the pivots when they rotate is responsible for a concentrated wearing of the bearings, so that the shape thereof undergoes ovalization. The stream then leaks into other volumes of the turbine engine, whose output decreases due to the gas leaks which occur. These disadvantages are even more marked if the sought compression ratio for the gases is high, because the thrust is greater and the faster wear results. Thus, in the presently known constructions, the envelope carrying the bearings of the pivots and which defines the stream or passage has a considerable rigidity and is made from steel, so that it is very heavy. The conventionally sought substitution of steel with titanium in order to lighten the structure is not possible here due to the temperature of the gases of the stream and the risks resulting therefrom of the titanium burning.